Command server: manually specify the list of temporary directory environment variable names

[phillco]

cursorless-dev/talon-rpc#4 resolves an issue (#966) caused by the fact of that Python and NodeJS sometimes check for different environment variable names based on platform. It resolves this by hardcoding the variables to match what Python does.

We should probably do the same (pin the list) on the Python side so that neither implementation is depending on implicit stdlib behavior, in case it changes in the future. Although, this does raise the question of how to know if we need to make changes in the future.

[nriley]

My feeling is we shouldn't fix what isn't broken. The Python behavior has been stable for decades — this list of environment variables was last modified in 1997, and all but some custom Windows fallbacks is at least 20 years old. If further problems develop we could make things more explicit.